Data communication networks may include various computers, servers, nodes, routers, switches, hubs, proxies, and other devices coupled to and configured to pass data to one another. These devices are referred to herein as “network elements,” and may provide a variety of network resources on a network. Data is communicated through data communication networks by passing protocol data units (such as packets, cells, frames, or segments) between the network elements over communication links on the network. A particular protocol data unit may be handled by multiple network elements and cross multiple communication links as it travels between its source and its destination over the network. Hosts such as computers, telephones, cellular telephones, Personal Digital Assistants (PDAs), and other types of consumer electronics connect to and transmit/receive data over the communication network and, hence, are users of the communication services offered by the communication network.
Network elements are typically implemented to have a control plane that controls operation of the network element and a data plane that handles traffic flowing through the network. The data plane typically will have a collection of line cards having ports that connect to links on the network. Data is received at a particular port, switched within the data plane, and output at one or more other ports onto other links on the network. To enable the data to be handled quickly, the data plane is typically implemented in hardware so that all of the decisions as to how to handle the data are performed using hardware lookups, etc.
Ports can fail for many reasons, including line card failure, failure of the link connected to the port (e.g. line cut), far-end line card failure, etc. The terms multi-link trunk (MLT), Link Aggregation Group (LAG) and logical ports are synonymous and these terms are used interchangeably. Likewise, the internal forwarding datapath within the network element may fail which may cause a port or set of ports to appear to have failed, or there may be some other failures along the logical/virtual connection to the port's external peer endpoint. There are numerous reasons why a port may fail.
In the event a port fails, traffic destined to the port should be diverted to flow out an alternate port to enable connectivity to be restored through the network. To minimize impact on the traffic being handled by the network element, e.g. to minimize down-time and packet loss, the quicker the rerouting of traffic can occur the better. Preferably, it would be advantageous to enable the traffic to fail over to an alternate port in under ten milliseconds (ms). Preferably, in the case of LAG or MLT, the traffic should be spread across the remaining ports rather than all moved from the failing port to a particular designated alternate port to prevent the designated alternate port from being overloaded with traffic.